Cathode



Aug. 3l, 1937.

H. HElNs 2,091,944?.4

CATHODE Filed Oct. 30, 1929 i! il. I ,0 `l ,3| /0 /7` :l: g /a\ Harald Heins I lNI/ENTOR.

,l @Y im ATTORNEY.

Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE CATHODE Application October 30, 1929, Serial No. 403,482

9 Claims.

This invention relates to cathodes of the indirectly heated type and adapted for use in vacuum rectifiers and electron discharge devices in general. The object of my invention is to more effectively support the heating member of such a cathode.

Referring to the drawing, Figure 1 is a view of a cathode. Figure 2'is an exploded view partly in section of the cathode.

The cathode in general consists of a hollow elongated member I preferably of nickel or any other suitable metal. If desired, this member may be of quartz or similar refractory insulating material. In either case, the outer surface of this member is suitably coated so that electron emission occurs upon heating. In order to provide connection for this electron emitting surface a lead 3 is welded to metallic member I or to the metal base portion under the coating if an insulating member is used. insulating plugs 4 and 5 of porcelain or any other suitable material are disposed at the ends of the metal member I. These plugs may be of any suitable shape to make a tight fit and are here shown as stepped. Plug 4 has two small apertures 6 and 'I through which pass the ends of a helical filament I0. This filament it will be noted is non-inductively wound and is composed of two portions II and I2 which are of helical shape and comprise both halves of the filament. In order to properly center the bottom of the filament, plug 4 is provided with an upstandng pinportion I3. In case member I is of metal, it is essential that the heating filament be maintained out of contact with the inner walls of this member. YIn order to do this, plug 5 has a wire member I2 passing through the center thereof and bearing a small hook I5 on the end thereof.

In order to assemble this cathode structure, plug 4 with its filament in place is inserted at one end of member I. I-Iook I5 attached to wire I2 is inserted at the other end of member I and caused to engage the loop at the top of the filament. Plug 5 is then threaded on wire I2 or may have been previously threaded thereon. After engaging hook I5 within the filament, wire I2 is retracted in order to pull the filament taut. To maintain this assembly, a collar IE of any suitable metal is welded to wire I2 beyond plug 5. A spring Il is disposed between collar I6 and plug 5 in order to maintain the filament taut at all times.

I claim:

1. A cathode, comprising a hollow tubular member having an outer electron emitting sur- (Cl. Z-27.5)

face, insulating plugs at each end of said member, one of said plugs having a central projecting portion, a helical filament carried by said plugs, one end of said filament surrounding said projecting portions, a rod passing through the other of said plugs, said rod carrying a member at one end engaging the other end of said filament, a spring surrounding said rod outside of said member and said plug, and means on said rod for anchoring the end of said spring remote from said plug whereby said rod tends to pull said filament taut.

2. A cathode structure comprising a hollow elongated member having an external surface adapted to emit electrons upon heating, insulating plugs closing the ends of said hollow member, a heating filament within said member, said filament comprising two series-connected helical portions, the terminals of said filament extending from one end off said hollow member and the respective convolutions of the two helical portions lying in substantially the same circumferential plane in relative parallel spaced relationship, one of said plugs carrying a rod-shaped insulating member extending part way toward the other of said plugs and supporting at least one turn of each of said helical portions atone end of said filament, the other of said plugs having means to support the other end of said filament.

3. A cathode structure comprising a hollow elongated metal member having an external surface adapted to 'emit electrons upon heating, insulating plugs closing the ends of said hollow member, a heating filament within said member, said filament comprising two series-connected helical portions, the terminals of said filament extending from one end of said hollow member and the respective convolutions of the two helical portions lying in substantially the same circumferential plane in relative parallel spaced relationship, one of said plugs carrying a rod-shaped insulating member extending into and supporting at least one turn of each of said helical portions at one end of said filament, the other of said plugs having means to support the other end of said filament, an unobstructed annular space being provided between the inner walls of said hollow member and said filament, whereby said walls may be heated by direct radiation from said filament.

4. A cathode structure comprising a hollow elongated metal member having an external surface adapted to emit electrons upon heating, insulating plugs closing the ends of said hollow member, a heating filament within said member, said filament comprising two series-connected helical portions, the terminals of said lament extending from one end of said hollow member and the respective convolutions of the two heli-- cal portions lying in substantially the same circumferential plane in relative parallel spaced relationship, one of said plugs carrying a rodshaped insulating member, at least one turn of each of said helical portions closely surrounding and engaging the surface of said rod-shaped member, whereby all of the turns of each helical portion are held spaced from each other, fthe other of said plugs having means to support one end of said lament, an unobstructed annular space being provided between the inner walls of said hollow member and said filament, whereby said walls may be heated by direct radiation from said filament.

5. A cathode structure comprising a hollow elongated metal member having an external surface adapted to emit electrons upon heating, an insulating plug closing one end of said hollow member, a heating filament within said member, said filament comprising two series-connected helical portions, the terminals of said filament extending from one end of said hollow member and the respective convolutions of the two helical portions lying in substantially the same circumferential plane in relative parallel spaced relationship, said plug carrying a rod-shaped insulating member extending part way toward the other end of said hollow member, at least one turn of each of said helical portions closely surrounding and engaging the surface of said rodshaped member, whereby all of the turns of each helical portion are held spaced from each other, an unobstructed annular space being provided between the inner walls of said hollow member and said filament, whereby said walls may be heated by direct radiation from said lament.

6. An electron emitting cathode of the indirectly heated type comprising a tubular metal sleeve member exteriorly coated with thermionically active material and an interiorly positioned double helical heater element electrically insulated therefrom, the terminals of said coil extending from one end thereof and the respective convolutions of the two helices lying in substantially the same circumferential plane in relative parallel spaced relationship, a small rod solely of insulating material extending from said one end of said tubular metal sleeve partway toward the other end of said tubular metal sleeve, at least one turn of each of said helices closely surrounding and engaging the surface of said rod, whereby all of the turns of each helix are held spaced from each other, an unobstructed annular space being provided between the inner walls of said hollow member and said heater, whereby said walls may be heated by direct radiation from said heater.

7. An electron emitting cathode of the indirectly heated type comprising a tubular metal sleeve member exteriorly coated with thermionically active material and an interiorly positioned non-inductive coil type heater element electrically insulated therefrom, said heater elementl comprising a double helical filament having the terminals extending from one end, the convolutions thereof lying in substantially the same circumferential plane, the respective turns of the helices lying in relatively close spaced parallel relationship to each other, a small rod solely of insulating material extending from said one end of said tubular metal sleeve partway toward the other end of said tubular metal sleeve, at least one turn of each of said helices closely surrounding and engaging the surface of said rod, whereby all of the turns of each helix are held spaced from each other, an unobstructed annular space being provided between the inner walls of said hollow member and said filament, whereby said walls may be heated by direct radiation from said filament.

8. An electron emitting cathode comprising a tubular metal sleeve member exteriorly coated with thermionically active material and an interiorly positioned non-inductive coil type heater element electrically insulated therefrom, said heater element comprising a twin coil filament having the terminals extending from one end the respective helices of said twin coil lying in relatively the same circumferential plane in parallel spaced relationship, with the turns of one helix lying in relatively close spaced relationship to the other, a small rod solely of insulating material extending from said one end of said tubular metal sleeve partway toward the other end of said tubular metal sleeve, at least one turn of each of said helices closely surrounding and engaging the surface of said rod, whereby all of the turns of each helix are held spaced from each other, an unobstructed annular space being provided between the inner walls of said hollow member and said filament, whereby said walls may be heated by direct radiation from said lament.

9. An electron-emitting cathode of the indirectly-heated type comprising a tubular metal sleeve member exteriorly coated with thermionically-active material, and an interiorly-positioned double helix heater element electrically insulated therefrom, the terminals of said coil extending from one end thereof and the respective convolutions of the two helices lying in substantially vthe same circumferential plane in re1- ative parallel spaced relationship, a` rod-shaped insulating member extending from one end of said tubular metal sleeve partway toward the other end of said tubularmetal sleeve, a portion only of the turns of each of said helices closely surrounding and engaging the surface of said rod-shaped member, the remainder of each of said helices being freely supported, an unobstructed annular space being provided between the inner walls of said hollow member whereby said walls may be heated by direct radiation from said heater.

HAROLD HEINS.

Cil 

